<chapter id="Glossary">
<title>Glossary</title>

<para>In this chapter you will find an explanation of most of the <quote>uncommon</quote> words that are used in the handbook.</para>

<glosslist>
<glossentry id="degrees">
<glossterm>degrees</glossterm>
<glossdef><para>Degrees are units to measure angles or turns. A full turn is 360 degrees,  a half turn 180 degrees and a quarter turn 90 degrees. The commands <userinput>turnleft</userinput>, <userinput>turnright</userinput> and <userinput>direction</userinput> need an input in degrees.</para></glossdef>
</glossentry>

<glossentry id="input-output">
<glossterm>input and output of commands</glossterm>
<glossdef><para>Some commands take input, some commands give output, some commands take input <emphasis>and</emphasis> give output and some commands neither take input nor give output.</para>
<para>Some examples of commands that only take input are:
<screen>
forward 50
pencolor 255,0,0
print "Hello!"
</screen>
The <userinput>forward</userinput> command takes <userinput>50</userinput> as input. <userinput>forward</userinput> needs this input to know how many <glossterm linkend="pixels">pixels</glossterm> it should go forward. <userinput>pencolor</userinput> takes a color as input and <userinput>print</userinput> takes a string (a piece of text) as input. Please note that the input can also be a container. The next example illustrates this:
<screen>
$x = 50
print $x
forward 50
$str = "hello!"
print $str
</screen></para>

<para>Now some examples of commands that give output:
<screen>
$x = ask "Please type something and press OK... thanks!"
$r = random 1,100
</screen>
The <userinput>ask</userinput> command takes a string as input, and outputs the number or string that is entered. As you can see, the output of <userinput>ask</userinput> is stored in the container <userinput>x</userinput>. The <userinput>random</userinput> command also gives output. In this case it outputs a number between 1 and 100. The output of the random is again stored in a container, named <userinput>r</userinput>. Note that the containers <userinput>x</userinput> and <userinput>r</userinput> are not used in the example code above.</para>

<para>There are also commands that neither need input nor give output. Here are some examples:
<screen>
clear
penup
</screen>
</para></glossdef>
</glossentry>

<glossentry id="intuitive-highlighting">
<glossterm>intuitive highlighting</glossterm>
<glossdef><para>This is a feature of &kturtle; that makes coding even easier. With intuitive highlighting the code that you write gets a color that indicates what type of code it is. In the next list you will find the different types of code and the color they get in <link linkend="the-editor">the editor</link>.
<table>
<title>Different types of code and their highlight color</title>
<tgroup cols="3">
<tbody>
<row>
<entry>regular commands</entry>
<entry>dark blue</entry>
<entry>The regular commands are described <link linkend="commands">here</link>.</entry>
</row>
<row>
<entry>execution controlling commands</entry>
<entry>black (bold)</entry>
<entry>These special commands control execution, read more on them <link linkend="controlling-execution">here</link>.</entry>
</row>
<row>
<entry>comments</entry>
<entry>gray</entry>
<entry>Lines that are commented start with a comment characters (#). These lines are ignored when the code is executed. Comments allow the programmer to explain a bit about his code or can be used to temporarily prevent a certain piece of code from executing.</entry>
</row>
<row>
<entry>brackets {, }</entry>
<entry>dark green (bold)</entry>
<entry>Brackets are used to group portions of code. Brackets are often used together with <link linkend="controlling-execution">execution controllers</link>.</entry>
</row>
<row>
<entry>the <link linkend="learn">learn</link> command</entry>
<entry>light green (bold)</entry>
<entry>The <link linkend="learn">learn</link> command is used to create new commands.</entry>
</row>
<row>
<entry>strings</entry>
<entry>red</entry>
<entry>Not much to say about (text) strings either, except that they always start and end with the double quotes (").</entry>
</row>
<row>
<entry>numbers</entry>
<entry>dark red</entry>
<entry>Numbers, well not much to say about them.</entry>
</row>
<row>
<entry>boolean values</entry>
<entry>dark red</entry>
<entry>There are exactly two boolean values, namely: true and false.</entry>
</row>
<row>
<entry>variables</entry>
<entry>purple</entry>
<entry>Start with a '$' and can contain numbers, strings or boolean values.</entry>
</row>
<row>
<entry>mathematical operators</entry>
<entry>gray</entry>
<entry>These are the mathematical operators: <userinput>+</userinput>, <userinput>-</userinput>, <userinput>*</userinput>, <userinput>/</userinput> and <userinput>^</userinput>.</entry>
</row>
<row>
<entry>comparison operators</entry>
<entry>light blue (bold)</entry>
<entry>These are the comparison operators: <userinput>==</userinput>, <userinput>!=</userinput>, <userinput>&lt;</userinput>, <userinput>&gt;</userinput>, <userinput>&lt;=</userinput> and <userinput>&gt;=</userinput>.</entry>
</row>
<row>
<entry>boolean operators</entry>
<entry>pink (bold)</entry>
<entry>These are the boolean operators: <userinput>and</userinput>, <userinput>or</userinput> and <userinput>not</userinput>.</entry>
</row>
<row>
<entry>regular text</entry>
<entry>black</entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
</para></glossdef>
</glossentry>

<glossentry id="pixels">
<glossterm>pixels</glossterm>
<glossdef><para>A pixel is a dot on the screen. If you look very close you will see that the screen of your monitor uses pixels. All images on the screen are built with these pixels. A pixel is the smallest thing that can be drawn on the screen.</para>
<para>A lot of commands need a number of pixels as input. These commands are: <userinput>forward</userinput>, <userinput>backward</userinput>, <userinput>go</userinput>, <userinput>gox</userinput>, <userinput>goy</userinput>, <userinput>canvassize</userinput> and <userinput>penwidth</userinput>.</para>
<para>In early versions of &kturtle; the canvas was essentially a raster image, yet for recent versions the canvas is a vector drawing. This means that the canvas can be zoomed in and out, therefore a pixel does not necessarily have to translate to one dot on the screen.</para>
</glossdef>
</glossentry>

<glossentry id="rgb">
<glossterm>RGB combinations (color codes)</glossterm>
<glossdef><para>RGB combinations are used to describe colors. The <quote>R</quote> stand for <quote>red</quote>, the <quote>G</quote> stands for <quote>green</quote> and the <quote>B</quote> stands for <quote>blue</quote>. An example of an RGB combination is <userinput>255,0,0</userinput>: the first value (<quote>red</quote>) is 255 and the others are 0, so this represents a bright shade of red. Each value of an RGB combination has to be in the range 0 to 255. Here a small list of some often used colors:
<table frame="none">
<title>Often used RGB combinations</title>
<tgroup cols="2" colsep="5" rowsep="1">
<colspec colname="c1"/>
<tbody>
<row><entry><userinput>0,0,0</userinput></entry><entry>black</entry></row>
<row><entry><userinput>255,255,255</userinput></entry><entry>white</entry></row>
<row><entry><userinput>255,0,0</userinput></entry><entry>red</entry></row>
<row><entry><userinput>150,0,0</userinput></entry><entry>dark red</entry></row>
<row><entry><userinput>0,255,0</userinput></entry><entry>green</entry></row>
<row><entry><userinput>0,0,255</userinput></entry><entry>blue</entry></row>
<row><entry><userinput>0,255,255</userinput></entry><entry>light blue</entry></row>
<row><entry><userinput>255,0,255</userinput></entry><entry>pink</entry></row>
<row><entry><userinput>255,255,0</userinput></entry><entry>yellow</entry></row>
</tbody>
</tgroup>
</table>
</para>
<para>Two commands need an RGB combination as input: these commands are <userinput>canvascolor</userinput> and <userinput>pencolor</userinput>.</para></glossdef>
</glossentry>

<glossentry id="sprite">
<glossterm>sprite</glossterm>
<glossdef><para>A sprite is a small picture that can be moved around the screen. Our beloved turtle, for instance, is a sprite.</para>
<para>Note: with this version of &kturtle; the sprite cannot be changed from a turtle into something else. Future versions of &kturtle; will be able to do this.</para></glossdef>
</glossentry>

</glosslist>

</chapter>
